Manual dispensing of a specific quantity of liquid or solid chemical into a body of water is common in industrial and residential applications. Adding laundry detergent to a clothes washer or anti-streaking wetting agent to the dishwasher are only two everyday residential examples. Consumers of appliances such as these are always searching for features that save them time and increase performance. Frequently, the feature of greatest value to the time strapped consumer is automation of the dispensing activity. Automation is highly valued by consumers since, in the examples cited above, it eliminates the need for messy manual volumetric measuring but more importantly, it removes the possibility that chemical dispensing was forgotten prior to initiating the activity.
The hot tub or pool is another example of an application where chemicals are routinely dispensed into a body of water, typically manually. In the case of a hot tub, water chemistry is critical for maintaining water sanitation and ultimately, water safety. Currently consumers are asked to regularly (at least bi-weekly) measure the condition of the water and then manually dispense an appropriate amount of a water treatment chemical or chemicals into the water. While some consumers are willing or able to accomplish this task religiously, it is well known that many residential tubs are not maintained appropriately. Mycobacteria: Health Advisory, United States Environmental Protection Agency, Office of Science and Technology, EPA-822-B-01-007 (August 1999). In some cases this can result in serious water quality conditions that can expose users to infectious bacteria such as mycobacteria (Id.). The main reasons these tubs are poorly maintained is consumer forgetfulness to address the water every two weeks and/or mistakes in dosing.
Given that a hot (100° F.-104° F.) body of water is significantly more susceptible to microbiological contamination, having a system that maintains superior water quality via automated water chemical dispensing into hot tubs would be a very high-value consumer product.
Further, due to the importance of proper recreational water maintenance, many pool and spa treatment systems have been developed in the past. For example, U.S. Pat. No. 4,992,156 discloses a pool purifier based on electrolytic production of chlorine. A bromine-generating system for portable spas is described in U.S. Pat. No. 6,238,555. It also uses an electrolytic cell for electrochemical bromine production, but employs an amperometric sensor for accurate determination of bromine levels in spa water. The sensor output is then used to control the power supply, and in turn, the electrolytic cell, in order to maintain bromine levels in spa water within preset limits.
Although the system is effective in producing and maintaining bromine levels in portable spas, its' operation is based on adding salts to spa water, which can lead to corrosion of metallic spa components (heaters, pumps etc.). Bromine degrades upon exposure to sunlight and is not odor-free. Also, some people's skin is too sensitive to halogens, while others find presence of salts in water objectionable.
Accordingly, there is a need for liquid dispensing systems that accomplish the task of dispensing the proper dose of water treatment chemical(s) into a pool or hot tub, thereby eliminating the errors inherent in manual additions but at least equally important, and eliminating the possibility that dosing was not accomplished at the recommended interval.